Whole Cell Electrophysiology of Primary Cultured Murine Enterochromaffin Cells

Summary

Enterochromaffin (EC) cells comprise a small subset of gastrointestinal epithelial cells. EC cells are electrically excitable and release serotonin, yet difficulties in culturing and identifying EC cells have limited physiological studies. The method presented here establishes a primary culture model amenable to examination of single EC cells by electrophysiology.

Abstract

Enterochromaffin (EC) cells in the gastrointestinal (GI) epithelium constitute the largest subpopulation of enteroendocrine cells. As specialized sensory cells, EC cells sense luminal stimuli and convert them into serotonin (5-hyroxytryptamine, 5-HT) release events. However, the electrophysiology of these cells is poorly understood because they are difficult to culture and to identify. The method presented in this paper outlines primary EC cell cultures optimized for single cell electrophysiology. This protocol utilizes a transgenic cyan fluorescent protein (CFP) reporter to identify mouse EC cells in mixed primary cultures, advancing the approach to obtaining high-quality recordings of whole cell electrophysiology in voltage- and current-clamp modes.

Introduction

The gastrointestinal (GI) epithelium is a diverse community consisting of several cell types. Enteroendocrine cells comprise roughly 1% of all epithelial cells, and enterochromaffin (EC) cells are the largest enteroendocrine cell population¹. Recent studies show that enteroendocrine² and EC^3,4 cells are electrically excitable. We are interested in understanding primary EC cell electrophysiology. Thus, the purpose of this study was to establish primary EC cell cultures optimized for whole cell electrophysiology.

Existing EC cell lines t....

Protocol

All methods described here have been approved by the Institutional Animal Care and Use Committee (IACUC) of Mayo Clinic. The primary cell culture portion of this protocol is based on previously published methods that can be referenced for further details¹⁰. All experimental procedures must be approved by the (IACUC), and all experiments must be performed in accordance with relevant guidelines and regulations.

1. Culture Preparation

1. Media.
   1. Prepare EC cell complete culture media with high glucose [4500mg/L] Dulbecco's Modified Eagle Medium (DMEM) supplemented with 5% Fetal B....

Results

Cultures:
Primary murine epithelial cells made from a transgenic Tph1-CFP model attach to dishes after 4 hours and are ready for physiological experiments between 24 to 72 h. When culture conditions had not been optimized, the epithelial cell culture consisted of large clumps, floating cellular debris, damaged membranes, and weak CFP signal in the EC cells (Figure 1A). Cultures that have been optimized for electrophysiolo.......

Discussion

Fully understanding EC cell function requires a high-quality primary culture method to generate cells for whole cell electrophysiology. Primary cultures of GI epithelium had traditionally been difficult due to low survival. Alleviating this confounding factor, the present method yields cultures of singular EC cells from either small or large bowel that are capable of surviving for several days.

We found that the following were critical for improving the quality of cultures to be suitable for e.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
100 mm x 15 mm culture dish	Corning (Falcon)	351029
Transfer Pipette	Fisherbrand	13-711-7M
10 mL serological pipette	Corning (Falcon)	357551
50 mL Conical	Corning (Falcon)	352098
15 mL Conical	Corning (Falcon)	352097
1,000 mL Barrier Pipet Tips	Thermo Scientific (Art)	2079E	Keep sterile
MatTek Glass Bottom Dishes	MatTek Corporation	P35G-1.5-14-C	Keep sterile
Micro-dissection Forceps - Very Fine, Extra-Long Points	Fine Science Tools	SB12630M
Surgical Scissors-Sharp	Nasco	14002-14
Micro-Dissection Scissors	Nasco	SB46568M
Monoject Hypo Needle, 21 G x 1" A, 100/BX	Covidien	8881250172
Tg(Tph1-CFP)1Able/J Mice	Jackson	Stock # 028366	Use male or female mice between the ages of 4-7 weeks
Microfil nonmetallic syringe needles (34 gauge, 67 mm)	World Precision Instruments	MF34G-5
Parafilm "M" Laboratory Film	Pechiney Plastic Packaging
R6101	Dow Corning
6 mL syringe with regular luer tip	Monoject
3 mL syringe with regular luer tip	Monoject
Electrophysiology Equipment
Amplifier	Molecular Devices	Axopatch 200B
Data acquisition system (daq)	Molecular Devices	Digidata 1440A
Signal conditioner	Molecular Devices	CyberAmp 320
Software	Molecular Devices	pClamp 10.6